Announcement

Collapse
No announcement yet.

Balcony cantilever

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Balcony cantilever

    This may be beyond the scope of this forum, but i'll ask anyway.

    My home has a 20' by 4' recessed balcony on the front of our second floor. It is water proofed and overtop of living space.

    We would like to extend this by at min 2 feet creating a 20' by 6-8' balcony.

    My understanding is that in order to cantilever these joists they would have to be sistered back into the house by a 3-1 ratio. this is not a concern should we open it up and be able to slide 12 foot 2x10s back into the house 5 feet (+4 over the recessed deck) and then cantilever beyond the exterior wall by 3 feet.

    However, my assumption (will have to open up below to be sure) is that because this wall does not extend all the way down through the first level, that there is some sort of beam/rim joist.

    If this is the case, does anyone have a solution for accomplishing this cantilever with only a 4 foot span to work with? I have seen people say that joist hangers can be employed upside down, attached to the rim joist, but I don't imagine this means I can cantilever more than 1' 4", 1/4 the joist span, not really worth all the trouble.

    I have used a local engineer in the past and will have my plan ok and any permit pulled by him, I just want to limit his consultation to a simple signing off.

    thanks.
    Last edited by Jaison; 10-10-2018, 01:07 PM.
  • Thread Continues Below...

  • #2

    Re: Balcony cantilever

    If I'm understanding you properly there better be something there to prevent the joists from twisting under the outside wall if nothing else. If it were simple blocking it would be easier to slide a new joist in to double up what's there. Obviously more info required to consider any good response.
    "Do it Right!"

    Comment


    • #3

      Re: Balcony cantilever

      I agree with Rusty, more info, drawings and a few pictures could go a long way into collecting the info you want before you approach the engineer.
      Steve The Drill Sergeant
      Check out MyShopNotes on YouTube.

      Comment


      • #4

        Re: Balcony cantilever

        thanks for the responses. I actually had a good discussion after posting this with someone more knowledgeable than I. Rusty, you are right. Either there is a rim joist or there is blocking in between the hoists to support the wall above. We basically determined that either way we could create a path to slide in the sister joists and then just block back in around these. A simple bolt on solution (hangers or cantilever brackets) I was hoping for seems non-existent and a custom engineered solution would just be too expensive. the only trouble then is opening up the drywall inside to secure the joists.

        Thanks.

        Comment


        • #5

          Re: Balcony cantilever

          It's a big job and not an easy one. If you continue there are no easy ways to do it so plan on ripping out a floor or a ceiling and then be prepared for issues of consequence regarding insulating and air and water leaks etc.

          Is it at all possible to support a larger deck on columns or corbels? Either way you're going to have to love that deck. BTW,,,,one of the downfalls is the extension will screen out more light.
          "Do it Right!"

          Comment


          • #6

            Re: Balcony cantilever

            Even if you could just slide the sistered joists in, the "sistering" part involves fastening the joists together. Usually that means driving nails every 16". So you would need to be able to access the sides of those joists along their entire span, not just be able to slide them in from the end.

            Another question is insurance. Back when I was building, we had one job where we had to retrofit support posts under a cantilevered deck. Most of the houses on that street had been built during the 70s with the same cantilevered second story deck. But several of them had run into the same problem as our customer: the insurance company no longer wanted to cover such decks. Notwithstanding the building code's allowance for them, the insurance company deemed the risk of collapse simply too high. The building code is, of course, simply the minimum standard, and both the municipality and interested parties such as your insurance company are free to insist on a higher standard. All that to say, it may be worth a call to your insurance company.

            Comment

            • Thread Continues Below...

            • #7

              Re: Balcony cantilever

              If your insurance is covering it now I would certainly not ask them about it.
              Rob

              Comment


              • #8

                Re: Balcony cantilever

                Originally posted by callee View Post
                Even if you could just slide the sistered joists in, the "sistering" part involves fastening the joists together. Usually that means driving nails every 16". So you would need to be able to access the sides of those joists along their entire span, not just be able to slide them in from the end.

                Another question is insurance. Back when I was building, we had one job where we had to retrofit support posts under a cantilevered deck. Most of the houses on that street had been built during the 70s with the same cantilevered second story deck. But several of them had run into the same problem as our customer: the insurance company no longer wanted to cover such decks. Notwithstanding the building code's allowance for them, the insurance company deemed the risk of collapse simply too high. The building code is, of course, simply the minimum standard, and both the municipality and interested parties such as your insurance company are free to insist on a higher standard. All that to say, it may be worth a call to your insurance company.
                Question,,,,,Would their refusal to insure change if that deck was called a balcony?
                "Do it Right!"

                Comment


                • #9

                  Re: Balcony cantilever

                  As I addressed in my response, I’m aware of the need to open up drywall to inspect and secure the joists from underneath. I plan to use pl premium and 16d nails every 12-16”, or whatever the engineer specs. This is mostly in the garage so not a big deal.

                  The balcony will be water proofed with 60mil single ply membrane as it is now. Existing flashing will hopefully be retained or replaced in the same way. So the joists will not be exposed in any way. It will also be under the existing overhang, albeit now out as far as the overhang, instead of three feet short.

                  I was hoping for someone to provide advice on a corbel design, but I have not been able to find any definitive information. I would be perfectly fine with 3 corbel brackets holding a beam and will definitely have this discussion with the engineer should he prefer this method. It is not the preferred look, aesthetically, however.

                  again, in my first post I said this will all be run through a sructural engineer, as I have done in the past. He pulls the permit, signs off on the work and files with the city.

                  I see the insurance aspect but find this hard to believe. There are many homes being designed today where whole floors cantilever over the first level. I will not be calling my insurance company, as I trust my engineer will provide me with the right guidance.

                  Appreciate the thoughts. I am committed to this project, however, it is very much in the preliminary stages o bviously
                  Thanks again.
                  Last edited by Jaison; 10-11-2018, 01:34 PM.

                  Comment


                  • #10

                    Re: Balcony cantilever

                    Originally posted by Jaison View Post
                    As I addressed in my response, I’m aware of the need to open up drywall to inspect and secure the joists from underneath. I plan to use pl premium and 16d nails every 12-16”, or whatever the engineer specs. This is mostly in the garage so not a big deal.

                    The balcony will be water proofed with 60mil single ply membrane as it is now. Existing flashing will hopefully be retained or replaced in the same way. So the joists will not be exposed in any way. It will also be under the existing overhang, albeit now out as far as the overhang, instead of three feet short.

                    I was hoping for someone to provide advice on a corbel design, but I have not been able to find any definitive information. I would be perfectly fine with 3 corbel brackets holding a beam and will definitely have this discussion with the engineer should he prefer this method. It is not the preferred look, aesthetically, however.

                    again, in my first post I said this will all be run through a sructural engineer, as I have done in the past. He pulls the permit, signs off on the work and files with the city.

                    I see the insurance aspect but find this hard to believe. There are many homes being designed today where whole floors cantilever over the first level. I will not be calling my insurance company, as I trust my engineer will provide me with the right guidance.

                    Appreciate the thoughts. I am committed to this project, however, it is very much in the preliminary stages o bviously
                    Thanks again.
                    Your choice, of course. I'm just not sure why you would expect an engineer to know what an insurance company will or will not elect to cover? And engineer can tell you whether or not it is properly engineered, but whether or not it is properly engineered is not the only criteria the insurance company uses.

                    Anyone with a wood stove in their shop, for example, has probably experienced this distinction first hand. My wood stove was properly set up and evaluated by a certified WETT inspector, I have the paperwork to prove it. Yet when I was doing my insurance renewal this year, many of the companies I called (more than half of them) refused to insure a wood working shop with a woodstove in it. They did not care about the fact that my wood stove was properly certified, they cared only about their own judgment that it was nevertheless too high a risk.

                    Hopefully your insurance company has no concerns about cantilevered decks. (Especially since you intend to build it before checking with them). But I know for a fact that some insurance companies do have a problem with them, and if your company is one of those, you could find yourself with a real headache at some point in the future. Or you could not. Who knows? It's a risk though. I personally wouldn't take it, but like I said, it's your choice.

                    Comment


                    • #11

                      Re: Balcony cantilever

                      Sorry, i did not intend to be dismissive. I think you bring up a valuable point and something i have never run into or heard of (I am admittedly young and inexperienced). Not something i am ingoring my any means. in fact this is exactly why i post on these forums -- to open my eyes to things i would of otherwise not considered.

                      Much more research is in order before i even get to the planning stage and this is definitely a consideration. thank you.

                      Comment

                      • Thread Continues Below...

                      • #12

                        Re: Balcony cantilever

                        I guess the question remaining is: what is an acceptable cantilever in deck building? No one ever stops their joists directly on the beam. Is it not acceptable to span joists between beams, how is maxing out span distance between beams any different? You make these calculations based on available data. I get that insurance companies are simply covering themselves, but I am only taking about 3 feet, 1/4 the joist span. The rule of thumb was 1/3 for years..

                        The example diagram, from my cities building dept, shows a cantilever, no more than i am proposing as far as ratios are concerned. Should everyone who builds a deck per these specs be calling in their insurance company to provide a letter of insurability?

                        Not arguing your valid point, just for discussions sake.
                        Attached Files

                        Comment


                        • #13

                          Re: Balcony cantilever

                          Jaison there is no reason that you cannot support a beam on corbels!! Quite likely you could get away with two not three. If you can support living space above a 16 or 18 foot wide garage door you can do the same in this instance. The critical factor is the strength of the beam sitting on the corbels versus the load above. You will have virtually no load above. you will have to provide substantial structural proof regarding the corbels but if you slide in new joists and bolt them in 2 or 3 ply scenarios the corbels would become decorative. Now add a strip of 1/4 inch plate steel between your joists and bolt that sandwich together and obviously no one could argue it's integrity. Now if I knew exactly where the corbels could be placed I could expand on their structural requirements but I'm sure your engineer is up to that detail.
                          "Do it Right!"

                          Comment


                          • #14

                            Re: Balcony cantilever

                            Originally posted by callee View Post

                            Your choice, of course. I'm just not sure why you would expect an engineer to know what an insurance company will or will not elect to cover? And engineer can tell you whether or not it is properly engineered, but whether or not it is properly engineered is not the only criteria the insurance company uses.

                            Anyone with a wood stove in their shop, for example, has probably experienced this distinction first hand. My wood stove was properly set up and evaluated by a certified WETT inspector, I have the paperwork to prove it. Yet when I was doing my insurance renewal this year, many of the companies I called (more than half of them) refused to insure a wood working shop with a woodstove in it. They did not care about the fact that my wood stove was properly certified, they cared only about their own judgment that it was nevertheless too high a risk.

                            Hopefully your insurance company has no concerns about cantilevered decks. (Especially since you intend to build it before checking with them). But I know for a fact that some insurance companies do have a problem with them, and if your company is one of those, you could find yourself with a real headache at some point in the future. Or you could not. Who knows? It's a risk though. I personally wouldn't take it, but like I said, it's your choice.
                            Ryan if I remember correctly you were able to insure your shop subsequently even with the stove. Is my memory correct and did the age of your building come into question at all? i ask because I can't foresee the instance where Jaison's balcony creates the risk you have with a wood stove. in your other description of second story decks what was it that the Insurance declined to insure against?
                            "Do it Right!"

                            Comment


                            • #15

                              Re: Balcony cantilever

                              What's the worst case scenario if you consult with your insurance company before the project? They refuse to insure the deck and you have to find a company that does or if you can't find one, you modify the design to one that can be insured. What's the worst case scenario if you don't? You have a claim and they refuse it. I think the advice not to talk to your insurance is poor advice. In the end it's your decision.

                              Comment

                              Working...
                              X